This three arm, randomized, double-blind trial will compare the efficacy and safety of chronic (12 months) oral administration of 256U87 (the prodrug of acyclovir) to acyclovir tablets for the suppression of recurrent ano-genital HSV infections in HIV-infected patients. Two groups will receive 256U87 (either 500mg BID or 1000mg q D); the third group will receive acyclovir 400mg BID.